The long-term goal of this project is to improve the impact of early intervention for antisocial aggression in childhood. Intensive parent training is the chosen treatment mode. A problem which severely limits the overall effectiveness of a parent training program is insufficient participation by a significant proportion of parents. This project involves a detailed analysis of initial dropout, ongoing dropout, and quality of participation for nondropouts in a sample of at least 150 families who are offered parent training. To qualify, the family must be seeking treatment for a boy between 4 and 9 years of age who is diagnosable as moderate to severe Undersocialized Conduct Disorder (Aggressive Type). The program involves individual training of pinpointing and tracking, reinforcment methods, use of timeout, reduction of physical punishment, appropriate use of antecedent procedures, improvement of the home social climate, specific skills for improving the child's style with peers, and instructions in how to analyze new problems. After assessment, families are randomly assigned to either of two treatment conditions: (1) conventional parent training, or (2) conventional parent training plus strategy for parental expectations. The two treatment approaches will be compared with respect to dropout rate, reasons for dropout, quality of participation, relationship between quality of participation and outcome, and outcome. Outcome measures include parental and teacher tracking of problem behaviors, and teacher ratings of peer relations. Additionally, training-session audiotapes will be rated by blind observers to verify fidelity of treatment conditions. Based on the analyses of dropout and participation, a model of participation will be developed and specific treatment recommendations will be offered to counter these problems. By understanding and improving the participation of families, early intervention can be successful with a greater proportion of hyperaggressive children who need treatment.